1. Field of the Invention
The present invention relates to a processing method of a silicon substrate.
2. Description of the Related Art
Currently, a microfabrication technique for semiconductor devices is applied to process a silicon substrate for a liquid ejection head. Further, there is a need in recent liquid ejection recording apparatuses for improvement in printing performance such as high-resolution and high-speed printing. Accordingly, a more accurate placement of ejected droplets and a higher-speed liquid refilling are required.
As disclosed in Japanese Patent Application Laid-Open No. H10-146979, a common liquid ejection head for use in a liquid ejection printing system is provided on a silicon substrate which includes thereon a fine ejection orifice for ejecting droplets; a liquid flow path communicatively connected to the ejection orifice; an ejection energy generating unit disposed in a part of the liquid flow path. Further, the silicon substrate includes a common liquid chamber communicatively connected to the liquid flow path.
Further, another liquid ejection head is developed as disclosed in Japanese Patent Application Laid-Open No. 2009-137155. In the liquid ejection head disclosed in Japanese Patent Application Laid-Open No. 2009-137155, liquid flow paths communicatively connected to one ejection orifice are arranged symmetrically with the ejection orifice. Such a configuration allows the generated bubbles to grow equally on the left and right liquid flow paths. Thus, the droplets can be stably ejected from the ejection orifice in a perpendicular direction and can be accurately placed.
Specific examples of the method of forming the aforementioned liquid ejection head formed on a silicon substrate having a plurality of supply ports communicatively connected to a common liquid chamber include a method of performing the two etch step process on the silicon substrate as disclosed in U.S. Pat. No. 6,534,247. According to U.S. Pat. No. 6,534,247, first, a first crystal anisotropic etching is performed to form a depressed portion to form a common liquid chamber. Then, a second dry etching is performed on a bottom surface of the depressed portion to form a plurality of supply ports. Thus, the silicon substrate has a plurality of supply ports communicatively connected to a common liquid chamber formed in the depressed portion.